package way;

import java.util.Scanner;

public class Add {
    public static int add(int n) {
        if (n == 1) {
            return n;
        }
        return n + add(n - 1);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        System.out.println(add(n));
    }
}
